Most Recent Weekly Report: 25 January-31 January 2012

On 25 January CVGHM lowered the Alert Level for Lewotolo from 3 to 2 (on a scale of 1-4) based on decreased seismicity and visual observations during 5-15 January. During 5-15 January fumarolic plumes rose 200-500 m above the summit and incandescence was observed.

Most Recent Bulletin Report: December 2011 (BGVN 36:12)

December 2011-January 2012 seismicity, incandescence, and evacuations

Plumes and seismic activity at Lewotolo volcano, Indonesia, increased during December 2011 and early January 2012. Lewotolo has erupted potassic calc-alkaline lavas containing as an accessary phase in vessicle fillings, the rare, complex zirconium-titanium-oxide mineral zirconolite (Ca0.8 Ce0.2 Zr Ti1.5 Fe2+0.3 Nb0.1 Al0.1 O7; de Hoog and van Bergen, 2000). Lewotolo last erupted in 1951. All historical eruptions were small (Volcanic Explosivity Index, VEI 2) with the exception of the first recorded eruption, which took place in 1660 and was as large as VEI 3. According to de Hoog and van Bergen (2000), strong fumarolic activity at the summit of Lewotolo indicates the presence and degassing of a shallow magma chamber.

December 2011-January 2012 activity increase. According to the Center of Volcanology and Geological Hazard Mitigation (CVGHM), Lewotolo produced thick white plumes reaching 50-250 m above the summit during December 2011. Seismicity increased on 31 December, and intensified on 2 January 2012 with tremor commencing at 1400. Accordingly, CVGHM raised the Alert Level from 1 to 2 (on a scale from 1-4) at 1800 on 2 January. Between 1800 and 2300 the same day, the maximum amplitude of recorded seismicity increased, and at 2000, incandescence was noticed at the summit.

At 2330 on 2 January, CVGHM increased the Alert Level to 3. Under the recommendation of CVGHM, access was prohibited within 2 km of Lewotolo (Hazard Zone III, figure 1), and residents in villages SE of the volcano were advised to keep vigilant and secure a safe place to flee to one of the towns to the N, W, or S in the event of an eruption.

Residents decide to evacuate. According to Antara News, evacuations began on 4 January spurred by increased activity of the previous few days, as well as minor ash falling in the villages. Antara News stated that most of the residents went to Lewoleba, the closest city to the volcano (~15 km to the SW of the summit). Of the evacuees in Lewoleba, all but about 50 people were reported to have found temporary housing with other residents of the city.

On 5 January, Channel 6 News reported that around 500 residents had evacuated leaving their homes in villages surrounding Lewotolo. They noted that residents who evacuated did so on their own accord, as the government had not yet called for evacuation. The Deputy District Chief of Lembata, Viktor Mado Watun, said “Black smoke columns are coming out of the mountain’s crater, the air is filled with the smell of sulfur while rumbling sounds are heard around the mountain.”

According to UCA News on 9 January, the health of the evacuees was cause for concern. Father Philipus da Gomez stated that “there are many refugees who have started suffering from acute respiratory infections.”

On 15 January, direct observation of the crater was made, and revealed incandescence in solfataras, a weak sulfur smell, and hissing sounds in both the N and S side of the crater. CVGHM especially noted that the N side of the crater was quite different than when it was last observed in June 2010, when no solfataras were present. Differential Optical Absorption Spectroscopy (DOAS) measurements revealed fluctuating and increasing SO2 flux between 11-90 tons/day during 8-16 January.

Weekly Reports - Index

Weekly Reports

25 January-31 January 2012

On 25 January CVGHM lowered the Alert Level for Lewotolo from 3 to 2 (on a scale of 1-4) based on decreased seismicity and visual observations during 5-15 January. During 5-15 January fumarolic plumes rose 200-500 m above the summit and incandescence was observed.

According to news articles, 500 people have evacuated their homes on 6 January because of increased activity at Lewotolo. Black smoke rose from the crater and rumbling sounds were reported. On 2 January CVGHM raised the Alert Level from 2 to 3 (on a scale of 1-4).

CVGHM reported that white plumes rose 50-250 m above the summit of Lewotolo during the month of December. Seismicity increased on 31 December and intensified on 2 January, the same day incandescence was observed. Based on visual and seismic observations, CVGHM raised the Alert Level from 1 to 2 (on a scale of 1-4) on 2 January, then later that day raised the Alert Level to 3.

Bulletin Reports

All information contained in these reports is preliminary and subject to change.

Plumes and seismic activity at Lewotolo volcano, Indonesia, increased during December 2011 and early January 2012. Lewotolo has erupted potassic calc-alkaline lavas containing as an accessary phase in vessicle fillings, the rare, complex zirconium-titanium-oxide mineral zirconolite (Ca0.8 Ce0.2 Zr Ti1.5 Fe2+0.3 Nb0.1 Al0.1 O7; de Hoog and van Bergen, 2000). Lewotolo last erupted in 1951. All historical eruptions were small (Volcanic Explosivity Index, VEI 2) with the exception of the first recorded eruption, which took place in 1660 and was as large as VEI 3. According to de Hoog and van Bergen (2000), strong fumarolic activity at the summit of Lewotolo indicates the presence and degassing of a shallow magma chamber.

December 2011-January 2012 activity increase. According to the Center of Volcanology and Geological Hazard Mitigation (CVGHM), Lewotolo produced thick white plumes reaching 50-250 m above the summit during December 2011. Seismicity increased on 31 December, and intensified on 2 January 2012 with tremor commencing at 1400. Accordingly, CVGHM raised the Alert Level from 1 to 2 (on a scale from 1-4) at 1800 on 2 January. Between 1800 and 2300 the same day, the maximum amplitude of recorded seismicity increased, and at 2000, incandescence was noticed at the summit.

At 2330 on 2 January, CVGHM increased the Alert Level to 3. Under the recommendation of CVGHM, access was prohibited within 2 km of Lewotolo (Hazard Zone III, figure 1), and residents in villages SE of the volcano were advised to keep vigilant and secure a safe place to flee to one of the towns to the N, W, or S in the event of an eruption.

Residents decide to evacuate. According to Antara News, evacuations began on 4 January spurred by increased activity of the previous few days, as well as minor ash falling in the villages. Antara News stated that most of the residents went to Lewoleba, the closest city to the volcano (~15 km to the SW of the summit). Of the evacuees in Lewoleba, all but about 50 people were reported to have found temporary housing with other residents of the city.

On 5 January, Channel 6 News reported that around 500 residents had evacuated leaving their homes in villages surrounding Lewotolo. They noted that residents who evacuated did so on their own accord, as the government had not yet called for evacuation. The Deputy District Chief of Lembata, Viktor Mado Watun, said “Black smoke columns are coming out of the mountain’s crater, the air is filled with the smell of sulfur while rumbling sounds are heard around the mountain.”

According to UCA News on 9 January, the health of the evacuees was cause for concern. Father Philipus da Gomez stated that “there are many refugees who have started suffering from acute respiratory infections.”

On 15 January, direct observation of the crater was made, and revealed incandescence in solfataras, a weak sulfur smell, and hissing sounds in both the N and S side of the crater. CVGHM especially noted that the N side of the crater was quite different than when it was last observed in June 2010, when no solfataras were present. Differential Optical Absorption Spectroscopy (DOAS) measurements revealed fluctuating and increasing SO2 flux between 11-90 tons/day during 8-16 January.

Geological Background

Anchoring the eastern end of an elongated peninsula that is connected to Lembata (formerly Lomblen) Island by a narrow isthmus and extends northward into the Flores Sea, Lewotolo rises to 1423 m. Lewotolo is a symmetrical stratovolcano as viewed from the north and east. A small cone with a 130-m-wide crater constructed at the SE side of a larger crater forms the volcano's high point. Many lava flows have reached the coastline. Historical eruptions, recorded since 1660, have consisted of explosive activity from the summit crater.

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Synonyms

Gunungapi | Ililewoto | Ngapi | Zwavelberg | Tokajain | Ililewotolo

Photo Gallery

Lewotolo volcano, rising here above the village of Jontona, anchors the eastern end of the northern peninsula that is connected to Lembata (formerly Lomblen) Island by a narrow isthmus. The symmetrical stratovolcano contains a small cone with a 130-m-wide crater constructed at the SE side of a larger crater that forms the volcano's summit. Many lava flows have reached the coastline. Historical eruptions, recorded since 1660, have consisted of explosive activity from the summit crater.

Photo by Kasturian, 1981 (Volcanological Survey of Indonesia).

Lewotolo, seen here from the Flores Sea NW of the volcano, anchors the eastern end of the northern peninsula that is connected to Lomblen Island by a narrow isthmus. Many lava flows have reached the coastline of the peninsula. Historical eruptions from Lewotolo have been recorded since 1660 and have consisted of explosive activity from the summit crater.

Photo by Rob McCaffrey, 1982 (Rensselaer Polytechnic Institute).

Four volcanoes are seen in this NASA Space Shuttle image (with north to the upper left) of Solor (lower left), Adonara (upper left), and Lembata (right) Islands. Ililabalekan volcano on SW Lembata (formerly Lomblen) Island is the only one of these without historical eruptions, although fumaroles are found near its summit. A satellitic cone was constructed on the SE flank of the steep-sided volcano, and four craters, one of which contains a lava dome and two small explosion pits, occur at the summit of Mount Labalekan.

References

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.

WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.

EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).